Poster: Plant-pathogen interactions

Abs # 568: Profiling Differential Gene Expression of Grape Plants in Response to the Infection of Xylella fastidiosa Using cDNA-AFLP

Presenter:	Lin, Hong , hlin@fresno.ars.usda.gov
Authors	Lin, Hong  (A)   Takahashi, Yuri  (B)   Hu, Rong  (B)   Walker, Andrew M. (B)
Affiliations:	(A): Agricultural Research Service, USDA (B): University of California, Davis

Pierce’s disease (PD), caused by Xylella fastidiosa (Xf), is one of the most devastating diseases of grapevines. The pathogen is a xylem-limited gram-negative bacterium that blocks xylem vessels, leading to death of the infected plant. Resistance to this disease exists in grape species and resistant cultivars have been bred. However, the molecular bases of pathogenesis and resistance are poorly understood. We used cDNA-AFLP to analyze the gene expression profile of PD infected grapevines. Our studies compared gene expression of highly susceptible and resistant siblings selected from a segregating population of Vitis rupestris x V. arizonica. Samples for cDNA-AFLP were prepared from mRNAs which were isolated from leaf, shoot and stem tissues of infected plants over the following time course: one day after inoculation, 4 days later, one week later and then seven 2 week intervals at which point susceptible plants fully expressed PD symptoms. cDNA-AFLP fragments were separated by polyacrylamide sequencing gels. Comparing the profiles of resistant and susceptible genotypes identified fragments representing up- and down-regulated genes. About 100 differentially expressed cDNA-AFLP fragments were collected, sequenced and annotated. These fragments reflect the differentially expressed genes from various tissues at different stages of PD development. To further study genes involved in the host-pathogen interaction at different stages of disease development, we designed a Taq-Man gene expression assay to analyze selected genes for their spatial and temporal expression in response to Xf infection. This study will help identify genes involved in the defense response and signaling/recognition cascade in PD susceptible and resistant grapes.